All of the tests so far, including those done by members on this site - to elicit the ignition of powder via an electrical spark, have failed- interstingly enough. That is why Harry said - "the more superstitious". I've also never seen a spark generated by rubbing two pieces of can steel together. Perhaps it can be done, but perhaps not by merely screwing on a cap.
I've once thought GOEX shipping 25 pounds of black powder in a large plastic bag, was asking for trouble. Now, I don't even give it a second thought as I pour from that 25 pound bag into a squeezed metal 3-pound coffee can, then into steel 1 pound GOEX cans on a steel scale, then cap with the steel GOEX caps. Maybe I should?